Method of producing hollow objects of compressed metallic powder.



. C. A. PFANSTIEHL. METHOD OF PRODUCING HOLLOW OBJECTS OF COMPRESSEDMETALLIC POWDER. APPLICATION FILED N 1 286,089. Patented Nov. 26, 1918.

k mm 257 r 17 6 /4 7 6 ED STATES PATENT OFFICE,

CARL A. PFANSTIEHL, OF HIGHLAND PARK,- ILLINOIS, ASSIGN OR TO PFANSTIEHLCOM- PANY, INCL, OF CHICAGO, ILLINOIS, A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Nov. 26, 1918.

Application filed. November 4, 1916. Serial No. 129,602.

T all whom it may concern:

Be it known that I, CARL A. PFANs'rIEHL, a citizen of the United States,residing at Highland Park, in the county of Lake and nesium oxid,tantalum oxid and thorium oxid and many other substances are useful intheir compressed form as dishes in which to perform certain chemicaloperations, as heating elements in' which to melt chemicals or metals.Some of these materials,

especially tungsten and tungsten oxid, but

many other materials to a less extent, resist flow during thecompressingoperation, that is, unless means are provided for compressing thematerial in substantially straight lines the material will become morehighly compressed at one point than another, and will therefore be weakor porous at the points of less compression.

It has been found that tungsten powder and other powders, the particlesof which are very hard, can be pressed into solid homogeneous objects byso distributing the tungsten or other powder under the movable part ofthe press that in the final position of the press all parts of thepowder have received the same amount of compression. This is morereadily accomplished where the article to be formed is rectangue lar inshape, since when in that shape only one of the dimensions of theloosely packed powder needs to be changed by the compression. 1

The pressure under which tungsten and some other powders are convertedinto solid homogeneous articles is about one hundred thirty to onehundred sixty tons per square inch. At such a pressure as this copperwill flow and can even be squirted in a manner similar to that in whichlead pipe-and cable sheaths are made. By embedding a piece of copper inthe powdered tungsten or other material to be compressed the copper byits propertyof flowing exerts :1 lat eral pressure upon the materialbeing com pressed and thus overcomes the characteristic of the tungstenor other powder which prevents it from flowing under pressure.

It has been found that although copper at the pressure of one hundredthirty tons per square inch and over will readily flow to equalizepressures throughout the powdered material being compressed,nevertheless the tenacity of the copper is such as to prevent it. frombeing forced into the pores of the powdered material under compression.

The shape of the copper invariably changes during the compressingoperation and the final shape to be secured must be determined byexperimenting with different shaped copper inserts. Obviously, there arelimitations to the shape which can be secured by means of the copper,but it has been found that almost any form of smoothly outlined interiorcan be produced by this process.

The materials whichI prefer to use in making chemical dishes and thelike are not readily attacked by the ordinary acids, whereas copper isreadily attacked. The copper may therefore be removed by the useof'nitric acid or if the powder be such as is attacked by nitric acidthe copper may be removed by some other acid which does not attack thecompressed powder.

One form of my invention and one method of carrying it out "areillustrated in the accompanying drawing, in which- Figure 1 represents acollapsible die and itsplunger filled with material for compression andalso having the copper insert therein;

Fig.2 is a section of the materialafter compression; and

Fig. 3 is a perspective view of the material after the copper insert hasbeen eaten out by the acid.

Similar characters of reference refer to similar parts throughout theseveral views.

The die illustrated herein forms no part of my present invention, thisdie being the subject matter of my co-pendin application, Serial No.124,504., filed ctober 9, 1916, and entitled Means and method forcompressing tungsten powder.

A die block 5 preferably of cast steel is provided with a plurality ofremovable members 6 having sloping faces which engage correspondinglysloping faces of the die block. The members 6 are made of the hardesttool steel of which are also made the base member 7 and plunger 8. Thebase 6 member 7 rests upon an insert 9 of steel which is somewhat harderthan the cast steel block '5 but somewhat softer than the base member 7.Likewise the plunger 8 is carried in a supporting block 10 of steel [0which is somewhat softer than the plunger 8, but which is somewhatharder than the press member 11 in which the member 10 is supported.Suitable end members not shown are provided, these end members be- '15ing likewise formed with'sloping faces op posing 'the faces forming thewalls of the die proper.

The rectangular chamber formed within the four walls and base of the dieis filled to the top with powder 13 to be compressed. The copper insert14 is then forced into the powder-until the upper and straight'face ofthe copper insert is flush with the top of .t'he die members 6. Theplunger 8 is then operated preferably by means of an oil pump' and apressure of substantially one hundred and fifty tons per square inch isexerted on the powder and copper. This pressure causes the copper tochange its form and to thus exert a lateral pressure substantially equalto the downward pressure exerted by the plunger. After the compressingoperation the pressure on the die members 6 is relieved by backing offthe screws 16 and 17, thus permitting the cross bar 18 to rise slightly,at the same time the pressure upon the plunger 8 is relieved, andthecompressed material is allowed to expand. This expansion occurs 40substantially equally in all directions, thus preventing the cracking ofthe compressed material.

The bar of material 19 with the copper 20 therein is placed in acid, thecopper being thus -removed. The compressed material may then be Washedand dried and used in its compressed form, or maythereafter be sinteredby passing through 'it an electric current sufficient to bring the metalto its welding temperature. Of course, if oxids are used they cannot besintered in this manner, but if either metallic tungsten powder ormetallic tantalum powder or in factany metallic powder is used, thearticles may be sintered into solid metal. It is not always possible toperform this sintering 0peration by passing the electric currentdirectly through the compressed material, becausethe material may byreason of its shape have greater cross section at some points than atothers, by reason of Which the resistance would be greater at .somepoints than at others. The compressed object may, however, be supportedupon a cradle of suitable material such as tungsten rods, whereon thecompressed article may be brought to a temperature suflicient to causethe particles to become sintered together.

Although'but one form of compressed ob ect is herein illustrated, it mayreadily be seen that other forms can be made by merely changing theshape of the die and the shape of thecopper insert. It is possible alsoto use other metals than copper, though some of the softer metals suchas lead cannot readily be used, because the lead will be forced Into thepores of the compressed material long beforethe necessary pressure hasbeen reached to create a solid homogeneous article. WVhen the soft metalis later eaten out of the pores the compressed material is I left porousand therefore unfit for some purposes. If for any reason porous articlesare desired, however, they may be constructed by the use of lead orother very soft metals.

Having thus described my invention, what I- claim as new and desire tosecure by Letters Patent of the United States is:

1. The method of producing, hollow articles of compressed metallicpowders which consistsin inserting a metal part having the property .toflow'under the pressure ofcompression, compressing the powder and metalpart and thereafter removing the metal part by the action of acids.

2. The method of producing hollow articles of compressed tungsten,tantalum, magnesium oxid, thorium oxid or the oxids of tungsten andtantalum which consists in inserting a metal part within the unpackedpowder to be compressed, compressing the powder about the metal part andthereafter

